The present invention relates to a vacuum cleaning folding rail for folding a stock web substrate, more particularly, a vacuum cleaning folding rail for the paper making industry for supplying a vacuum to remove loose matter from a web substrate under tension during folding.
Equipment for completing folds in high-speed web processes are well known in the art. Folding formers, folding plates, and xe2x80x9cVxe2x80x9d-folders are machined and polished sheet metal elements over which a web substrate is guided. A typical xe2x80x9cVxe2x80x9d-folder would consist of a generally triangular structure that would include a substantially trapezoidal folding plate surface that initially receives the moving web substrate. A folding plate is a generally flat surface with a pair of spaced-apart converging edges. A substantially trapezoidal transition nose surface is contiguous to and merges smoothly with the surface of the fold plate, forming an oblique angle therewith. A folding plate generally has a terminal nose surface contiguous to the transition nose surface and merges smoothly therewith forming an oblique angle with it. The terminal nose portion terminates in a point that defines the location of the fold.
However, when a web substrate passes over such a folding plate structure, the process of folding imparts work to the web substrate and results in a drag on the web substrate. The drag and bending of the web substrate may tend to abrade or scrape coating or actual web fiber from the web substrate. This loss of coating or web substrate fibers tends to be cumulative, and over time, a highly packed and dense layer forms on the folding plate surface. This hard-packed layer must be removed physically by scraping, or by chemical treatment. This involves shutting down a line for an indefinite period to allow personnel access and time to remove any packed matter.
Such a folder is shown in Dutro, U.S. Pat. No. 3,111,310. Dutro discloses a complex series of folding plates for making a fold in a web or ribbon of paper. Curved flanges bound the converging edges of the fold plate and transition nose surfaces. A flue is formed integrally within the flanges. Dutro uses conventional folding plate technology resulting in the potential build-up of loose particulate emanating from the web onto the folding plate surface.
German Patent No. DE AS 2,240,397 discloses a former for longitudinally folding paper webs processed in a rotary paper machine having a funnel shaped nose plate and nose. Positive pressure is applied to a passing web substrate, ostensibly to reduce friction. However, contact by the web with the forming plate is still present. Thus, drag is reduced, but not eliminated on nonporous materials causing the build-up of web fiber or web coating onto the folding plate. Loose substrate is not removed and can still build up onto the folding surface.
U.S. Pat. No. 5,094,658 discloses a plowshare folder in an envelope-forming machine where individual envelope blanks are conveyed through the folding mechanism by a vacuum table. The vacuum table includes a series of spaced apart conveyor belts that are driven over the surface of a vacuum table in the feed direction of the blanks. The vacuum table includes a plate having apertures that draw in air as a result of a vacuum created by the evacuation of air from a vacuum plenum created below the surface of the vacuum plate. The plowshare folder includes a thin wall of rigid material having at the front end an initial planar surface that gradually bends in a 180xc2x0 turn. Through the 180xc2x0 turn, blades of the plowshare engage the seal flap region of the envelope blank. The flaps to be folded extend parallel to the axis of movement of the blank across the vacuum table and are folded into overlying relation with the main body of the blank.
The folding operation in U.S. Pat. No. 4,994,010 is performed by a plowshare-type folding mechanism that includes fold loops and folding blades. During the folding operation, the lateral flaps converge and are glued together in an overlapping area by means of an adhesive layer that has been previously applied with the result that the folded and overlapping flaps form the backside of the envelope. The lateral flaps are simultaneously folded by folding blades that have an inner curvature that evolves from an initial point where the side flaps extend horizontally to a point where the flaps are folded in a tubular configuration. The guide surfaces of the folding blades curve progressively through 180xc2x0 along travel of the blank.
Similarly, other patents show the use of folding plates in various configurations. However, none seek to remove loose substrate or coating from the passing web. Exemplary patents include: German Patent Nos. DE AS 1,142,878 and DE AS 2,163,408, English Patent GB 862,296, and U.S. Pat. Nos. 4,131,271; 4,321,051; and 5,779,616.
Accordingly, it would be desirable to provide a device for folding a web substrate that minimizes web line cleaning time while providing a high quality finished product.
In a non-limiting exemplary embodiment of the present invention, an elongate rail for an equal path folder comprises a hollow tube having a longitudinal axis, a proximate and a distal end, and a vacuum applied thereto. The tube has first and second substantially planar surfaces parallel to the longitudinal axis, and forming an edge therebetween. There is at least one opening in the rail angularly positioned away from the first and said second surfaces. The vacuum causes a negative pressure to be applied to the opening so that web substrate, under tension, such as various paper type materials and the like as well as various types of plastic web materials which are capable of longitudinal movement, passing over the first and second surfaces has at least a portion of the vacuum applied to a surface of the web when the web is proximate to at least one of the first and second surfaces.
In yet another alternative embodiment of the present invention, an elongate rail for an equal path folder comprises a hollow tube having a longitudinal axis, a proximate and a distal end, and a vacuum applied thereto. The tube has a first substantially planar surface parallel to the longitudinal axis, having a protuberance and an opening disposed thereon. The rail has a second substantially planar surface parallel to the longitudinal axis. The first and said second surfaces form an edge therebetween. The vacuum causes a negative pressure to be applied to the opening so that a web substrate passing over the first surface has at least a portion of said vacuum applied to a face of said web substrate when said web substrate is under tension and is proximate to said first surface.
In still another alternative embodiment of the present invention, an equal path folder comprises at least two elongate rails, each rail comprising a hollow tube having a longitudinal axis, a proximal end, a distal end, and a vacuum applied thereto. Each tube has a first and second substantially planar surface parallel to the longitudinal axis, forming an edge therebetween. There is at least one opening in the tube angularly positioned away from the first and second surfaces. The first surface being angularly convergent upon the second surface at the distal end to form an edge therebetween, and, the vacuum causing a negative pressure to be applied to said opening so that a web substrate under tension and passing over the first and second surfaces has at least a portion of said vacuum applied to a face of the web substrate when the web substrate is proximate to at least one of the first and second surfaces. A first of the two elongate rails can be a mirror image of a second of the at least two elongate rails, and, wherein the distal end of the first elongate rail is fixably positioned relative to the distal end of the second elongate rail wherein the distal end of the first elongate rail and the distal end of the second elongate rail form an edge therebetween.
The advantages and novel features of the present invention will become apparent to those skilled in the art from the following detailed description, which simply illustrates various modes contemplated for carrying out the invention. As will be realized, the invention is capable of other different aspects and geometries, all without departing from the scope of the invention. Accordingly, the following drawings and descriptions are illustrative in nature and not restrictive.